remove unnecessary includes
code style cleanups. no functional changes.
move an irssi utility function to a separate file
move tcl core/intepreter functionality to separate file
reload scripts by restarting interpreter.

also add a license file
move signal setup to the module core.

also re-order signal callback functions to match
the order we load/unload them.
match re-ordering in signals.h as in signals.c
move irssi command functions into a separate file
don't print directly to irssi from tcl core functions
be more careful with interpreter/parameter state in tcl core
remove unnecessary include